The aim of the research project is to study reperfusion injury occurring after reoxygenation of previously ischemic hearts. This study aims to evaluate the cause, physiologic and biochemical effect, time course, and reversibility of reperfusion injury by modifying reperfusate ionic composition and mode of delivery in acute and chronic animal studies. The role of reperfusate calcium, pH, cardioplegia, and perfusion pressure will be studied in nonhypertrophied and hypertrophied hearts.